A conventional machine position control device has been configured to enhance stability of its control system using, as a feedback signal for the position controller, a signal obtained by summing up signals obtained by low-pass filtering a load-position signal as a load-position detection value, and by high-pass filtering a motor-position signal as a motor-position detection value: a motor-position signal with no phase delay in a frequency band over its resonance frequency where the phase delay of the load-position signal becomes significant, because a driving system using a motor has a limited rigidity (for example, refer to Patent Document 1).
Moreover, in another conventional machine position control device, a pre-compensator is provided therein which configuration enables high-accurate control with a deformation error along moving directions of a machine system being compensated, by adding to an input parameter, a signal, as a feed-forward compensation value, obtained by multiplying by a gain the second order differential value of the input parameter (for example, refer to Patent Document 2).
[Patent Document 1] Japanese Laid-Open Patent Publication No. 2004-334772 (FIG. 1)
[Patent Document 2] Japanese Laid-Open Patent Publication No. 1999-184529 (FIG. 3 and FIG. 4)